Charged air coolers are used in a manner known per se for the purpose of cooling the air that is compressed by the turbocharger and/or for cooling an air mixture of fresh air and exhaust gas that is being recycled. As the air and/or the air mixture cool down, it is possible for moisture, for example water, from the air and/or air mixture to condense in the intake tract of the internal combustion engine, in particular in the charged air cooler. The condensate must be removed from the intake tract in order to prevent the liquid condensate from passing from the intake tract into the internal combustion engine and damaging the internal combustion engine and/or damaging parts of the systems, for example as a result of corrosion.
A system for collecting and discharging condensate that forms in a charged air cooler of a chargeable internal combustion engine is, for example, known from US 2010/0229549 A1. The condensate is supplied to a reservoir by way of an outlet pipe that is connected to the charged air cooler on a bottom face. A reservoir outlet that can be closed by means of a valve is located on the bottom face of the reservoir. The level of condensate in the reservoir is determined by means of a fill level sensor. In order to prevent charged air from escaping from the charged air cooler by way of the outlet pipe into the reservoir and from escaping from said reservoir by way of the reservoir outlet as the condensate is discharged, the valve is only opened if the condensate fill level in the reservoir exceeds a predetermined minimum fill level. If there is at least the minimum level of condensate in the reservoir, a control unit that controls the valve opens the valve when particular operating conditions prevail in the internal combustion engine. In order to prevent the reservoir from overflowing, it is possible to provide a further fill level sensor that detects a maximum condensate fill level in the reservoir and the control unit causes condensate to be discharged from the reservoir as soon as the maximum condensate fill level is achieved. The system described renders it possible to discharge condensate from the reservoir without in so doing allowing charged air to escape from the charged air cooler, said system does, however, require at least one and/or two additional condensate fill level sensors for detecting the condensate fill level in the reservoir.
Furthermore, a condensate discharge device is known from WO 2007/069972 A1, wherein condensate can be discharged from a charged air cooler by means of said condensate discharge device. An orifice is provided for this purpose in a base of the charged air cooler, which orifice can be opened and closed by means of a closing element, wherein the closing element, for example a bimetal element, is controlled in dependence upon a temperature. The condensate discharge device described does not prevent charged air from escaping from the charged air cooler by way of the orifice that is opened in a predetermined temperature range.
On the basis of this background, the object of the present invention is to provide a method for discharging condensate from a turbocharger arrangement. In one example, the method may include opening a drain valve positioned within a condensate reservoir, the condensate reservoir fluidly coupled to an intake tract downstream of a charge air cooler (CAC) and then closing the drain valve in response to a pressure difference between the intake tract and ambient air decreasing below an initial pressure difference, the initial pressure difference determined before opening the drain valve, by a threshold amount. In another example, the drain valve may be closed in response to an air-fuel ratio decreasing below an initial air-fuel ratio, the initial air-fuel ratio determined before opening the drain valve, by a threshold amount. In yet another example, the drain valve may be closed in response to a mass air flow (MAF) in the intake tract upstream of the reservoir increasing above an initial mass air flow, the initial mass air flow determined before opening the drain valve, by a threshold amount. In some examples, the drain valve may be opened at pre-determined time intervals during engine operation. In other examples, the drain valve may only open during stead-state engine operating conditions wherein the pressure difference, air-fuel ratio, and or MAF may not be expected to change. In this way, the method allows for condensate that forms in the turbocharger arrangement to be discharged in a reliable manner while also reducing an amount of charged air escaping from the turbocharger arrangement as the condensate is discharged.
Moreover, the method is to be particularly simple to perform and in particular said method is not to require any additional components or is to require as few as possible additional components that are specifically required solely for performing the method. This object is achieved by virtue of a method having the features of claim 1. In addition, the subordinate claims disclose advantageous embodiments of the invention. It is to be noted that the features explained individually in the description hereinunder can be mutually combined in any technically expedient manner and disclose additional embodiments of the invention. The description additionally characterizes and specifies the invention in particular in conjunction with the figures.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.